Evolution of the characters 3a and 3b.

<p>(A) Character 3a, arrangement of the polyps (three states). (B) Character 3b, arrangement of the polyps (six states). I, II, and III, major clades cited in the text. The state of the analysed character is represented by a coloured pie, placed at each internal/terminal node of the tree. An enlarged multi-coloured pie is used when multiple states of a character occur at a specific node. In this latter case the size of each slice is proportional to the probability of occurrence of the state.